O'Fallon Water Hardness & Quality Report (2026)
Water Hardness
16.3 grains per gallon
Source
river
pH Level
8.5
neutral = 7.0
Lead
0.009 mg/L
✓ Below action level
TDS
736.4 mg/L
Est. Daily Cost
$0.74
energy & soap waste
Source: USGS Water Quality Portal · Updated 2026
0–60
mg/L
Soft
61–120
mg/L
Moderately Hard
121–180
mg/L
Hard
180+
mg/L
Very Hard
Appliance Damage Report
In O'Fallon, your appliances are currently losing 37% efficiency due to mineral buildup.
| Appliance | In O'Fallon | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 1.5 yrs | 8.5 yrs | -82% |
| Washing Machine | 3.3 yrs | 12 yrs | -73% |
| Water Heater | 5 yrs | 15 yrs | -67% |
Regional Water Comparison
How O'Fallon compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ O'Fallon, Missouri | 279 mg/L | 8.3 ppt | 🔴 Very Hard | river |
| Dardenne Prairie, Missouri | 289.5 mg/L | 8.5 ppt | 🔴 Very Hard | river |
| Saint Peters, Missouri | 137 mg/L | 4.6 ppt | 🟠 Hard | river |
| Lake Saint Louis, Missouri | 134.5 mg/L | 4.6 ppt | 🟠 Hard | river |
| Wentzville, Missouri | 267.5 mg/L | 8 ppt | 🔴 Very Hard | river |
National Benchmark
How O'Fallon compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ O'Fallon | 279 mg/L | 🔴 High |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes O'Fallon's Water Unique?
Local geology and source profile
O'Fallon, Missouri, in St. Charles County northwest of St. Louis — one of Missouri's fastest-growing cities — draws its municipal water supply from the Missouri River via the Missouri American Water Company (a subsidiary of American Water Works Company), regional water infrastructure serving St. Charles County. Missouri American Water treats Missouri River water and distributes throughout the O'Fallon and St. Charles County area. Water hardness reaches 279 mg/L — classified as very hard, substantially above Lee's Summit (180.5 mg/L) on the same Missouri River source system.
O'Fallon's significantly higher hardness compared to other Missouri American Water service areas reflects the St. Charles County intake and distribution zone characteristics. The Missouri River at the St. Charles County reach, just upstream of the Missouri–Mississippi confluence at St. Louis, has collected maximum mineral load from the entire 529,000-square-mile Missouri Basin — including the highly calcareous Platte River (Nebraska loess drainage), Kansas River (Kansas limestone drainage), and the upper Missouri from Montana's calcareous prairie. Additionally, the St. Charles County distribution system infrastructure and the local geology (the Ordovician Gasconade Dolomite and Roubidoux Formation of the Ozark Plateau, which underlies parts of St. Charles County) may contribute additional hardness through local groundwater blending.
At 279 mg/L, O'Fallon residents face significant hard water challenges throughout the home. Heavy scale deposits form rapidly on faucet aerators, showerheads, shower glass, and tile — monthly descaling with citric acid solution is essential maintenance. Dishwashers require rinse-aid plus periodic internal cleaning, and water heaters need annual professional inspection. Missouri American Water consistently delivers water meeting all Missouri DNR and EPA Safe Drinking Water Act requirements.
Geology & Source: River supply from the Missouri River via the Missouri American Water Company (American Water Works) regional system — the Missouri River system receives calcareous Pennsylvanian limestone, Cretaceous sedimentary, and Permian formations from the Missouri Basin; the St. Charles County distribution zone shows very hard supply at 279 mg/L — substantially harder than Lee's Summit (180.5 mg/L) on the same Missouri River source.